The studies described in this application have three interrelated purposes. (1) To examine and describe several fundamental structural and functional properties of developing nerve endings synaptic plasma membranes in the rat cortex. Special emphasis will be placed on developmental changes in the structure, composition, function, and organization of membrane proteins, glycoproteins and lipids. (2) To examine the effects of modifying postnatal hormone levels and to examine the effects of under-nutrition on the development of two synaptic functions: neurotransmitter transport and receptor binding. We will establish the duration of the vulnerable period after which time nutritional or hormonal rehabilitation can no longer effect recovery of synaptic function. (3) To analyze the information obtained in (1) and (2) and devise specific experiments which will simultaneously: (a) establish the developmental importance of the observed structural, compositional and organizational changes in synaptic macromolecules and lipids, and (b) characterize some of the deleterious effects that modifying the pup's hormonal and nutritional status has on synaptic development. The technical skills commensurate with successfully completing this study are evidenced by our publications.